In tracking a target and particularly a target at a low altitude, problems arise due to multi-path propagation. These problems have been known since the beginning of radar technology. Many attempts have been made to solve the problems especially at sea where it is important to be able to detect and follow missiles or rockets which move as close to the surface of the sea as a few meters, so-called "sea skimmers".
A distinguished overview of different methods and their shortcomings is found in D. K. Barton, Low-Angle Tracking, Proc. IEEE 62, No. 6, June 1974, pages 687-704. In S. M. Sherman, "Complex indicated angles applied to unresolved radar targets and multipath", IEEE Trans. Aerosp. Electron Syst., vol AES-7, January 1971, pages 160-170, where the utilization of complex angles in multi-path propagation is described. The present invention relates to a further development of this method.